Before answering your main question, I want to address whether or not Luke 21:22 and Isa 61:2 are necessarily talking about the same thing, in order to determine how much we should consider Isa 61:2 when interpreting Luke 21:22.
Is there an allusion to Isa 61:2 in Luke 21:22?
It appears that in the question, you're asserting that Jesus in Luke 21:22 is alluding to Isa 61:2. I haven't studied this in depth, but at the very least such an assertion would require some amount of evidence, especially since in contrast to Luke 4:19 where there is a clear quotation of the LXX, there is no such lexical similarity between Luke 21:22 and Isa 61:2. (By lexical similarity I mean using the same lexemes, the same words).
Compare the similarity between the NA27 text of Lk 4:18-19 and Rahlf's LXX:
Isa 61:1-2 LXX
Πνεῦμα κυρίου ἐπ᾿ ἐμέ, οὗ εἵνεκεν ἔχρισέν με· εὐαγγελίσασθαι πτωχοῖς ἀπέσταλκέν με, ἰάσασθαι τοὺς συντετριμμένους τῇ καρδίᾳ, κηρύξαι αἰχμαλώτοις ἄφεσιν καὶ τυφλοῖς ἀνάβλεψιν, καλέσαι ἐνιαυτὸν κυρίου δεκτὸν
πνεῦμα κυρίου ἐπ᾿ ἐμὲ οὗ εἵνεκεν ἔχρισέν με εὐαγγελίσασθαι πτωχοῖς, ἀπέσταλκέν με, κηρύξαι αἰχμαλώτοις ἄφεσιν καὶ τυφλοῖς ἀνάβλεψιν, ἀποστεῖλαι τεθραυσμένους ἐν ἀφέσει, κηρύξαι ἐνιαυτὸν κυρίου δεκτόν.
There are clear differences but enough lexical similarity (even apart from the fact that Jesus says He's quoting Isaiah) to know He's quoting Isa 61. So not to say that there needs to be 100% lexical similarity for there to be a quote or an allusion, but if there's not at least strong lexical similarity we would want to look for other indicators if we want to argue that there's an allusion or quotation happening (eg, see Echoes of Scripture in the Letters of Paul by Hays pg 29ff for a one list of criteria to use when determining if there's an allusion or not).
So then, comparing that to the similarity (or lack thereof) of NA27 Luke 21:22 and Rahlf's LXX Isa 61:2:
If it were just that one is plural and one is not, maybe there could still be an allusion. But since the word translated "vengeance" is different and even coming from different roots, I'm a bit hesitant. Even more than that, when there are only two words that are similar between two passages, we should be cautious in assuming there is an allusion being made necessarily, unless there are other factors involved (including possibly how rare those two words are, etc). Jesus might also be doing a direct translation/paraphrase of the Hebrew (which happens in other passages where we know there is an allusion), but if so we can only know there is an allusion being made from other factors.
Accordingly, I don't think we should consider a possible allusion to Isaiah 61:2 when interpreting the meaning of Luke 21:22, at least without further evidence. (Although well done keeping your eyes/ears peeled for potential allusions).
So then what events do Luke 21:22 refer to?
It seems that as far as timing goes, we have two major indicators of when these things happen:
- In Luke 21:20, Jerusalem's time has come near when it is surrounded by
- This time of desolation is said to endure until the times
of the Gentiles has been fulfilled (NA27 ἄχρι οὗ πληρωθῶσιν καιροὶ
We also have to take into account that by Jesus' description, these events will "to fulfill all that is written" (21:22), which seems to indicate a weighty event in my book!
Another factor to consider is that, especially when referring to prophecy but even otherwise, I tend to see if there's an OT backdrop/context that Jesus would share with His original audience, that both of them would understand. Like Mac's Musings in this answer, I would say that some of Daniel's prophecies seem to be more in the foreground of Jesus' thought here than Isa 61, especially in light of the fact that Jesus refers to Daniel in the parallel passage in Matthew 24:15 and alludes to the same passage in Daniel in Mark 13:14. Looking at Daniel also gives a potential answer for what the "times" (plural) of the Gentiles could be referring to, since prophecies in Daniel list out a series of times where nations have dominion over Israel (first Babylon, then Persia-Media, then Greece, then Rome). In Daniel, this series of eras (or "times" as the case may be...) then culminates in the end of Jerusalem's desolation, for there comes a rock which destroys these nations, establishing Jerusalem as the capital of the Kingdom of God on earth (cf. Dan 2). This is the direction Jesus continues in as well: from the desolation of Jerusalem under Gentile reign to the end of Gentile reign whereby the kingdom of the Messiah is established; cf. Luke 21:25-28, where Jesus alludes to Dan 7:13 by referring to the "Son of Man coming in a cloud with power and great glory" which culminates in redemption for God's people.
This fits the picture that Jesus describes in Luke as well. There is desolation in Jerusalem until the times of the Gentiles is fulfilled, at which point Jerusalem will no longer be desolate, exiled, or trampled underfoot by the Gentiles.
This fits the timeline presented by a number of other prophets as well, regarding the Day of the LORD. Jerusalem is exiled and under foreign rule until the Messiah returns, ends exile, and establishes his kingdom. This could explain why Jesus would say that this would "fulfill all that is written" (Lk 21:22).
So then what's the vengeance in 21:22?
I could see someone arguing it's referring to vengeance on Israel for their covenant unfaithfulness to God, perhaps particularly since they crucified their Messiah. But I could also see it referring to vengeance on both Israel and the nations, particularly since when the OT prophets talk about the Day of the LORD, it is a day of judgment against both Israel (eg Joel 2) and the nations (Obad 15). In other words, since the OT sometimes pictured God's judgment against the sin of the nations and the sin of Israel as two parts of the same coin, perhaps Jesus is doing the same thing here. (Of course, I'm begging the question of all kinds of interpretive issues related to the Day of the LORD...but there's also other examples where Israel and the nations are all pictured being judged together, eg Amos 1-2).
But how long does it all last?
Jerusalem had been likewise destroyed and exiled before by Babylon, which is what I'm arguing is the beginning of these "times of the Gentiles". As one of these times of the Gentiles, Jerusalem was under Roman reign, and would destroy Jerusalem in AD 70. These times of the Gentiles will end when the Son of Man returns in the clouds and establish His kingdom. This has still not occurred, and we see how this plays out currently, as Israel still does not have total control over the Temple mount in Jerusalem.
- Of course I recognize that there is no one single "LXX", since rather there are many Greek translations of the OT, but just using that terminology here for simplicity.
- Again, I am not contributing as someone who has studied this passage in depth but just to add to the conversation.
- I'm coming from a relatively conservative and Premillenial background. Not apologizing for that, but especially for a discussion like prophecy, presuppositions account for quite a bit. :)